CN111796244B - Evaluation method for influence of offshore wind farm on ground wave beyond-view-range radar detection efficiency - Google Patents
Evaluation method for influence of offshore wind farm on ground wave beyond-view-range radar detection efficiency Download PDFInfo
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- G—PHYSICS
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Abstract
The invention discloses an evaluation method for the influence of an offshore wind farm on the detection efficiency of a ground wave beyond-the-horizon radar. According to the ground wave beyond visual range radar parameters and the pre-selected area expansion scene analysis of the wind power plant, screening out objects needing to be subjected to key analysis; establishing a fan electromagnetic model according to the provided wind turbine generator parameters, and realizing the establishment of a single fan electromagnetic model; according to the longitude and latitude coordinates of the pre-built wind power plant fan and the relative position information of the radar, an array is built in FEKO electromagnetic calculation software, a scene model is built, and the shielding influence is analyzed; calculating RCS changes of single fan equipment in different states; analyzing the influence of Doppler frequency; deriving a multipath effect theoretical formula; and (5) carrying out actual measurement on the equivalent scene, and evaluating the influence range of the wind power plant by using electromagnetic environment noise data. The invention gives out quantitative evaluation results by adopting electromagnetic simulation calculation, theoretical derivation, actual measurement scene equivalence and other means.
Description
Technical Field
The invention belongs to the field of electromagnetic compatibility of wind power plants and radar systems, and particularly relates to an evaluation method of the influence of an offshore wind power plant on the detection efficiency of a ground wave beyond-the-horizon radar.
Background
In recent years, the number and the scale of wind farm construction planning in China are gradually increased, and particularly, coastal areas are greatly developing offshore wind power project construction. The offshore wind power resources are rich, and the method is a preferable position for constructing a wind power plant. However, the wind power plant has wide occupied area, large fan size and high fan blade rotating speed, and the marine target environment of the surrounding shore-based radar can be possibly changed. For sea detection radars, object shielding, diffraction and the like generated by a wind farm are all very adverse factors for the radar. Currently, countries and organizations such as the united states, the european union and the like have established assessment mechanisms for wind farm planning construction, mainly analyzing and solving the influence of wind farms on military facilities, and especially ensuring that the early warning detection capability of radars is not affected. The technical means mainly adopts an electromagnetic field simulation calculation method, an electromagnetic calculation simulation actual scene is utilized, and a quantitative result of the influence of the wind power plant on the radar detection efficiency is obtained. The domestic research on the problems of influence on electromagnetic environment, radar performance and the like of the wind farm is started later, the technical means is not perfect, and sufficient theoretical and technical support cannot be provided for planning and construction of the offshore wind farm.
The ground wave beyond-view distance radar realizes the detection of a remote beyond-view distance target by utilizing the diffraction propagation characteristic of the high-frequency electromagnetic wave along the surface of the earth, and the propagation path is curved along the surface of the earth instead of straight line propagation due to the diffraction action of the high-frequency electromagnetic wave along the sea surface, so that the detection distance can be extended to the shielding region of the curved surface of the earth. In order to make the diffraction propagation loss of high-frequency electromagnetic waves along the sea surface small, radar frequency is often operated at the low end of a short wave band, and vertical polarized waves are adopted. The offshore area within 50 km from land is generally selected for the offshore wind farm construction site, and the characteristics of special working frequency band, wide covered sea area and long coherent accumulation time of the ground wave beyond-view range radar are considered, so that the wind farm in the detection sector can influence radar detection performance.
Disclosure of Invention
The invention provides an evaluation method of the influence of an offshore wind farm on the detection efficiency of a ground wave beyond line of sight radar, which takes an offshore wind project to be constructed as an analysis object, and gives out quantitative evaluation results by adopting electromagnetic simulation calculation, theoretical derivation, actual measurement scene equivalence and other means.
The invention is realized by the following technical scheme:
an evaluation method of the influence of an offshore wind farm on the detection efficiency of a ground wave beyond visual range radar, the evaluation method comprising the following steps:
step 1: according to basic performance, station distribution position, beam width and action area parameters of the ground wave beyond visual range radar and pre-selected area expansion scene analysis of a wind power plant, eliminating radar which cannot be influenced or has very small influence by the wind power plant at all, and screening out objects needing key analysis;
step 2: establishing a fan electromagnetic model according to the provided wind turbine generator parameters, and realizing the establishment of a single fan electromagnetic model through grid division, grid quantity setting and grid optimization;
step 3: according to longitude and latitude coordinates of a pre-built wind power plant fan and relative position information of a radar, a wind power unit array is built in FEKO electromagnetic calculation software, a ground wave beyond visual range radar scene model is built, influences of a wind power plant area on surrounding electric field intensity are simulated, and shielding influences caused by wind power units are analyzed;
step 4: simulating and calculating RCS changes of single fan equipment in different states;
step 5: analyzing the influence of Doppler frequency generated by the rotation of the fan blade on radar echo;
step 6: deducing a multipath effect theoretical formula according to the distribution characteristics of the wind turbine generator array and calculating;
step 7: and (3) measuring equivalence of scenes, testing electromagnetic environment noise data in similar environments, performing equivalent calculation on the environment and power consumption of the wind power plant to be built, and evaluating the influence range of the wind power plant.
Furthermore, in the step 2, the wind turbine generator is composed of a tower, a hub, a cabin and blades, wherein the blades are made of nonmetallic materials, and reflected signal energy is small, so that the tower is used as a main modeling calculation object; meanwhile, lightning protection wires exist between the blades and the hub, so that the fan model is equivalent; the fan electromagnetic model is based on a curved surface modeling method, and the establishment of the geometric model is realized by combining CAD and Femap software according to fan parameters.
Furthermore, in the step 2, the grid division refers to that grids with different sizes are adopted at the positions of different structures, so that the whole structure shows different grid division forms of density, and when the grid is divided by the target geometric modeling, the arch height error generated by all plane elements on the actual curved surface is ensured to be smaller than 1/16 of the wavelength.
Further, the grid optimization in the step 2 refers to the rationality of the grid geometry, the quality will affect the calculation accuracy, the grid with poor quality will even stop the calculation, and each unit of the triangular grid is an equilateral triangle in ideal case.
Further, in the step 3, the ground wave beyond visual range radar scene model is established by setting a working wave band, beam direction and polarization mode according to the relative position of the radar and the wind power plant, and calculating the change condition of the electric field intensity of the peripheral area of the wind power plant, so as to obtain a direct shielding quantitative analysis result.
Further, the Doppler effect in the step 5 is that the fan blade rotates to enable the radar return wave band to have Doppler frequency shift component, the modulation depth is calculated by using the amplitude modulation signal of the radar signal after being modulated by the fan blade rotation frequency, and the Doppler effect is judged according to the amplitude ratio after modulation.
Further, in the step 6, the multipath effect is to derive and calculate the influence of the fan on the reflection of the radar electromagnetic wave by using a radar equation, the direct wave of the target reflection and the secondary reflection echo passing through the wind motor are synthesized at the receiving antenna, if the amplitude of the echo signal reflected by the wind motor is too large, the radar can be influenced to distinguish the target azimuth, then a false target is formed after the radar receiver is processed, the false alarm effect is caused, and the multipath effect influence range is analyzed according to the distance and the angle change among the radar, the target and the wind power plant.
Furthermore, in the step 7, an actually measured analysis method is adopted, and the actually measured method is carried out on similar built wind power equipment, so that the radiation characteristics of the wind power plant to be evaluated can be converted by carrying out equivalent calculation according to the unit type, the number, the arrangement positions and the regional wind power grade factors of the wind power plant aiming at noise comparison of different frequencies of different working states of the test environment fans.
The beneficial effects of the invention are as follows:
1. the invention adopts the MoM electromagnetic calculation method based on the integral equation, and the calculation result is more accurate; the method is easier to obtain for an actual radar system, can replace an actual radar test or a microwave darkroom shrinkage ratio test, and can save cost.
2. The invention analyzes from three aspects of shielding, radiation and scattering, and compared with the traditional analysis method, the invention has more comprehensive evaluation results and more accurate evaluation results.
3. The invention is more specific to the analysis of actual measurement scenes, performs reasonable equivalent calculation on parameters, and has more reference value for practical engineering application.
Drawings
FIG. 1 is a processing block diagram of an evaluation method of the influence of an offshore wind farm on the detection efficiency of ground wave beyond line of sight radar.
FIG. 2 is a schematic diagram of the position of the ground wave beyond line-of-sight radar and wind farm of the present invention.
FIG. 3 is a diagram of an equivalent electromagnetic simulation model of a blower of the present invention.
FIG. 4 is a graph of the electric field strength calculation around a wind farm according to the present invention.
Fig. 5 is a graph of electric field intensity for three azimuth angles of a wind farm according to the present invention.
Fig. 6 is a graph of the RCS values for three frequencies of a single fan of the present invention.
Fig. 7 is a schematic diagram of the noise test of the present invention.
Fig. 8 is a graph of radio noise measurement data versus various conditions of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1, for convenience of explanation, the following scenario is established:
the wind power plant comprises a square array of 25 fans, the interval between the fans is 500m, the capacity of each fan is 6MW, the capacity of the total assembly machine is 150MW, and the fan parameters are shown in Table 1:
TABLE 1 fan parameters
The position relation between the ground wave beyond visual range radar and the wind power plant is shown in figure 2, and the radar working frequency is selected from three frequency points of 4MHz,7MHz and 12 MHz.
Step 1: according to basic performance, station distribution position, beam width and action area parameters of the ground wave beyond visual range radar and pre-selected area expansion scene analysis of a wind power plant, eliminating radar which cannot be influenced or has very small influence by the wind power plant at all, and screening out objects needing key analysis;
step 2: establishing a fan electromagnetic model according to the provided wind turbine generator parameters, and realizing the establishment of a single fan electromagnetic model through grid division, grid quantity setting and grid optimization;
the wind turbine generator consists of a tower, a hub, a cabin and blades, wherein the blades are made of nonmetallic materials, and reflected signal energy is small, so that the tower is taken as a main modeling calculation object; as shown in fig. 3; meanwhile, lightning protection wires exist between the blades and the hub, so that the fan model is equivalent; the fan electromagnetic model is based on a curved surface modeling method, and the establishment of the geometric model is realized by combining CAD and Femap software according to fan parameters.
The grid division refers to the adoption of grids with different sizes at the positions of different structures, in order to adapt to the characteristic of surface current distribution, the grid with relatively dense is needed at the position with severe change of the surface current, in order to better reflect the change rule, and the grid with relatively sparse is needed at the position with smaller change, so that the grid division form with different densities is needed to be divided, the whole structure shows the grid division form with different densities, although the grid points on the surface of a target body generated by geometric modeling are surface 'accurate points', the size of the grid can influence the calculation result of a normal vector because the surface element of a small plane formed by three grid points is approximately used as the surface of the body when the grid discrete point calculation method vector, the arch height error caused by the small plane element instead of an original curved surface is generally called as being smaller than 1/16 of the wavelength of radar according to the influence analysis of the radar scattering cross section RCS.
How much the grid number is set directly influences the accuracy of the calculation result and the size of the calculation scale, generally, the grid number is increased, the calculation accuracy is improved, but the calculation scale is also increased, so that two factors should be weighed and comprehensively considered when determining the grid number.
Grid optimization refers to the rationality of the grid geometry, the quality will affect the calculation accuracy, the grid with poor quality will even stop the calculation, the triangle grid in the ideal case is an equilateral triangle, so that the minimum interior angle of the triangle unit becomes an important standard for measuring the quality of the grid, the larger the minimum interior angle is (the larger the triangle interior angle is required to be and fixed 180, the more the triangle should be close to the equilateral triangle, when the minimum interior angle of three angles is 60 degrees, the equilateral triangle is formed, at this time, the minimum interior angle cannot be larger), and the better the grid quality is.
Step 3: according to longitude and latitude coordinates of a pre-built wind power plant fan and relative position information of a radar, a wind power unit array is built in FEKO electromagnetic calculation software, a ground wave beyond visual range radar scene model is built, influences of a wind power plant area on surrounding electric field intensity are simulated, and shielding influences caused by wind power units are analyzed;
the method for establishing the ground wave beyond visual range radar scene model is to set working wave bands, wave beam directions and polarization modes according to the relative positions of the radar and the wind power plant, calculate the change condition of the electric field intensity of the peripheral area of the wind power plant, and accordingly obtain direct shielding quantitative analysis results.
The electric field intensity of the peripheral area after the electromagnetic wave passes through the wind power plant is analyzed, as shown in fig. 4. The cross-section of three of the orientations was selected and the calculation results are shown in fig. 5. Outside 2.5Km from the center of the wind power plant, the fluctuation amplitude of the electric field is within 0.1V/m, and the shielding signal-to-noise ratio is reduced by 0.83dB at maximum; outside 3.5Km from the center of the wind power plant, the fluctuation amplitude of the electric field is within 0.05V/m, and the shielding signal-to-noise ratio is reduced by 0.42dB maximally. Further, the variation amplitude is remarkably reduced beyond 2.5Km, and the flatness is promoted.
Step 4: simulating and calculating RCS changes of single fan equipment in different states;
the plane wave is vertically polarized, the incident direction is the direction away from the fan blade, the RCS value of the fan equivalent model fan blade rotating 0-120 degrees is calculated respectively, and when the frequency is 4MHz,7MHz and 12MHz, the RCS calculation result is shown in figure 6. The maximum of the individual blower RCS is reached at a maximum frequency of 12MHz and a peak value of 45.25dBm 2 。
Step 5: analyzing the influence of Doppler frequency generated by the rotation of the fan blade on radar echo;
the Doppler effect is that the fan blade rotates to make the radar return wave band have Doppler frequency shift component, the modulation depth is calculated by using the amplitude modulation signal of the radar signal after the fan blade rotating frequency modulation, and the Doppler effect is judged according to the amplitude ratio after modulation.
According to the maximum 15 revolutions per minute of the fan parameters, the maximum rotation frequency of the fan is 0.75Hz, namely at 4MHz,7MHz and 12MHz, the Doppler frequency shift is 0.75Hz, which is equivalent to the generation of false targets with radial movement speeds of 28.1m/s,12.5m/s and 7.5m/s on a radar screen; when the fan speed is below 15 rpm, decoys with different radial speeds still occur.
Let the radar signal after windmill rotation modulation be
U(t)＝V c (1+m cosω f t)cosω c t (1)
Wherein omega f =3pi/2 is the modulation signal angular frequency, V c For the amplitude of the carrier signal,for the modulation factor, V f Modulating signal amplitude omega c Is the carrier signal angular frequency. The frequency point with the largest amplitude difference is selected as a reference, namely, the frequency point with the largest amplitude difference is 4 MHz. Taking the average value of the individual blower RCS calculated in FIG. 6 as the carrier amplitude42.55dBm 2 A maximum point 41.535dBm different from the average amplitude 2 As the modulation signal amplitude.
The modulated signal is then expressed as:
calculated U max ＝21750，U min = 14250, the modulation depth was 20.8%.
Further analysis is made from the signal spectrum, the spectrum of the modulated signal being:
thus at a frequency of omega c At an amplitude of 18000 pi and at a frequency of ω c ±ω f The amplitude is 1875 pi, and the ratio of them is-9.8 dB. As the rotation frequency of the fan is between 0 and 0.75Hz, the maximum ratio of the two frequencies is-9.8 dB, the rotation of the fan can form false targets in a wind power field area, and the detection of the ground wave beyond visual range radar in the area is influenced.
Step 6: deducing a multipath effect theoretical formula according to the distribution characteristics of the wind turbine generator array and calculating;
the multipath effect is to deduce and calculate the influence of a fan on the reflection of a radar electromagnetic wave by utilizing a radar equation, the direct wave of a target reflection and the secondary reflection echo of the wind motor are synthesized at a receiving antenna, if the amplitude of an echo signal reflected by the wind motor is overlarge, the resolution of the radar on the target azimuth can be influenced, then a false target is formed after the radar receiver is processed, the false alarm effect is caused, and the multipath effect influence range is analyzed according to the distance and angle change among the radar, the target and the wind power plant.
Using the RCS maximum value of a single fan in fig. 6 as a reference value of 45.25dBm 2 Let the distance between the target and the radar be r 1 The distance between the wind power plant and the radar is r 2 The distance between the target and the wind farm is r 3 . Target objectScattered power P t The scattered signal reaches the receiving antenna directly, and the power density is as follows:
the other path of scattered signals reaches the wind power plant, and the power density is as follows:
the signals reach the receiving antenna through the wind farm, and the power density expression is as follows:
in the formula (6), N is the number of fans, and the ratio of the target scattering signal reaching the receiving antenna through the wind farm to the target scattering signal directly reaching the receiving antenna is:
the ratio is the influence caused by the wind turbine, so that the influence of the power density when the scattered signal reaches the radar can be obtained through calculation by the formula.
When the target distance is set to 5Km from the wind power plant, the number of fans is 25 at most in one resolution unit of the radar distance and the angle, and the direct wave is calculated according to the formula (7) and reaches the receiving antenna after passing through the wind power plant, wherein the direct wave is about 25.74dB compared with the target scattering signal. If the radar detection threshold is set to be 20dB, at the moment, the multipath scattered signals cannot form false targets, and the influence on a radar system is small. (mainly looking at the setting of radar detection threshold at the time, when the ratio of the direct wave to the multipath echo is greater than the detection threshold, the target direct wave signal can be detected at the moment, but the multipath echo can not be detected, so that a false target can not be generated).
Step 7: and (3) measuring equivalence of scenes, testing electromagnetic environment noise data in similar environments, performing equivalent calculation on the environment and power consumption of the wind power plant to be built, and evaluating the influence range of the wind power plant.
Because the internal structure of the wind motor is complex, the source of electromagnetic radiation is difficult to be defined, so that analysis cannot be performed through theoretical calculation, and only an actual measurement analysis method can be adopted. In addition, because the wind farm is not built in the evaluation stage, actual measurement can only be performed on similar wind power equipment which is built. Since the structure, size and working principle of the wind motor are approximately the same, the measured analysis of the radiation effect has versatility. After the actual measurement result of similar scenes is obtained, the radiation characteristics of the wind power plant to be evaluated can be converted by carrying out equivalent calculation on the relevant factors of the unit type, the number, the arrangement position and the regional wind power grade of the wind power plant.
The testing method comprises the following steps: a broadband active loop antenna is used as a test antenna, a handheld spectrometer is used as a test receiver, and the test principle is shown in fig. 7. The test environment is a built near-sea wind power plant, the offshore distance of the wind power plant is about 10Km, the offshore distance is about 13.4Km along the coastline direction, the capacity of the project assembly machine is 202MW, and 55 wind power units are erected altogether. And respectively selecting the wind turbine generator to be in a shutdown working state and a rotation working state for noise data measurement, wherein the test result is shown in figure 8.
Equivalent calculation: according to the actual measurement result, the average noise rise value of 13.1dB at 4-5 MHz is taken as the noise power increased compared with the starting and stopping of the wind turbine generator. The actual measured total capacity of the loader is 202MW, while the planned construction total capacity is 150MW, so the power is reduced by 1.29dB; the number of wind turbines in experimental data is 55, the number of wind turbines planned to be built is 25, the wind speed of the wind turbines in the working state of the wind turbines is 5.2m/s, the power is 0.5MW, the rated power of a fan planned to be built is 4MW, and the wind power level of a sea area to be built is considered to be different, and the wind power level needs to be converted to the maximum power for calculation, so that 5.61dB to be compensated is obtained through calculation; therefore, the wind turbine generator system is folded to a wind turbine generator system planned to be built, and the working noise of the wind turbine generator system is averagely raised by about 17.42dB in a rated power state. Electromagnetic wave power attenuation formula utilizing free space
Calculating, wherein f is the radar working frequency, r is the attenuation radius, G T G for transmitting antenna amplification gain R For receiving the antenna amplification gain, the attenuation radius is calculated to be about 7.43Km, namely, electromagnetic noise influence is negligible outside a circular area taking the center of the wind power plant as the center and taking 7.43Km as the radius.
Claims (9)
1. A method for evaluating the effect of an offshore wind farm on the detection efficiency of a ground wave beyond line-of-sight radar, the method comprising the steps of:
step 1: according to basic performance, station distribution position, beam width and action area parameters of the ground wave beyond visual range radar and pre-selected area expansion scene analysis of a wind power plant, eliminating radar which cannot be influenced or has very small influence by the wind power plant at all, and screening out objects needing key analysis;
step 2: establishing a fan electromagnetic model according to the provided wind turbine generator parameters, and realizing the establishment of a single fan electromagnetic model through grid division, grid quantity setting and grid optimization;
step 3: according to longitude and latitude coordinates of a pre-built wind power plant fan and relative position information of a radar, a wind power unit array is built in FEKO electromagnetic calculation software, a ground wave beyond visual range radar scene model is built, influences of a wind power plant area on surrounding electric field intensity are simulated, and shielding influences caused by wind power units are analyzed;
step 4: simulating and calculating RCS changes of single fan equipment in different states;
step 5: analyzing the influence of Doppler frequency generated by the rotation of the fan blade on radar echo;
step 6: deducing a multipath effect theoretical formula according to the distribution characteristics of the wind turbine generator array and calculating;
step 7: and (3) measuring equivalence of scenes, testing electromagnetic environment noise data in similar environments, performing equivalent calculation on the environment and power consumption of the wind power plant to be built, and evaluating the influence range of the wind power plant.
2. The method for evaluating the influence of the offshore wind farm on the ground wave beyond-view radar detection efficiency according to claim 1, wherein in the step 2, the wind turbine is composed of a tower, a hub, a cabin and blades, the blades are made of nonmetallic materials, and reflected signal energy is small, so that the tower is used as a main modeling calculation object; meanwhile, lightning protection wires exist between the blades and the hub, so that the fan model is equivalent; the fan electromagnetic model is based on a curved surface modeling method, and the establishment of the geometric model is realized by combining CAD and Femap software according to fan parameters.
3. The method for evaluating the influence of the offshore wind farm on the detection efficiency of the ground wave beyond visual range radar according to claim 1, wherein the grid division in the step 2 is that grids with different sizes are adopted at the positions of different structures, the whole structure shows different grid division forms of density, and when the grid is divided by the geometric modeling of the target, the arch height error of all plane elements on the actual curved surface is ensured to be smaller than 1/16 of the wavelength.
4. The method for evaluating the influence of the offshore wind farm on the detection efficiency of the ground wave beyond line of sight radar according to claim 1, wherein the grid optimization in the step 2 refers to the rationality of the grid geometry, the quality will influence the calculation accuracy, and the grid with poor quality will even stop the calculation.
5. The method for evaluating the effect of an offshore wind farm on the detection efficiency of ground wave beyond line of sight radar according to claim 4, wherein each cell of the triangular mesh is an equilateral triangle.
6. The method for evaluating the influence of the offshore wind farm on the detection efficiency of the ground wave beyond visual range radar according to claim 1, wherein the step 3 is characterized in that the ground wave beyond visual range radar scene model is established by setting a working wave band, a wave beam direction and a polarization mode according to the relative position of the radar and the wind farm, and the change condition of the electric field intensity of the peripheral area of the wind farm is calculated, so that a direct shielding quantitative analysis result is obtained.
7. The method for evaluating the effect of a wind farm on the detection efficiency of ground wave beyond visual range radar according to claim 1, wherein the Doppler effect in step 5 is that the rotation of a fan blade causes a Doppler frequency shift component in a radar return band, the modulation depth is calculated by using an amplitude modulation signal of a radar signal modulated by the rotation frequency of the fan blade, and the Doppler effect is judged according to the amplitude ratio after modulation.
8. The method for evaluating the influence of the offshore wind farm on the detection efficiency of the ground wave beyond visual range radar according to claim 1, wherein in the step 6, the multipath effect is to deduce and calculate the influence of a fan on the reflection of the radar electromagnetic wave by using a radar equation, the direct wave of the target reflection and the secondary reflection echo passing through the wind motor are synthesized at a receiving antenna, if the amplitude of the echo signal reflected by the wind motor is too large, the resolution of the radar on the target azimuth is affected, a false target is formed after the radar receiver is processed, the false alarm effect is caused, and the multipath effect influence range is analyzed according to the distance and the angle change among the radar, the target and the wind farm.
9. The method for evaluating the influence of the offshore wind farm on the ground wave beyond visual range radar detection efficiency according to claim 1, wherein in the step 7, an actually measured analysis method is adopted, actual measurement is carried out on similar wind power equipment which is built, noise comparison of different frequencies of different working states of a fan in a test environment is carried out, and the radiation characteristics of the wind farm to be evaluated can be converted by carrying out equivalent calculation according to the unit type, the number, the arrangement position and the regional wind power grade factors of the wind farm.
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